X-ray computed microtomography offers scientists and engineers a way to gain a better understanding of the materials with which they work. Under high magnification, it becomes evident that many materials (including rock and bone) have a porous microstructure that permits fluid flows. Such fluid flows are often of great interest, e.g., in subterranean hydrocarbon reservoirs. Accordingly, significant efforts have been expended to characterize materials in terms of their flow-related properties including porosity, permeability, and the relation between the two.
Scientists typically characterize materials in the laboratory by applying selected fluids with a range of pressure differentials across the sample. Such tests often require weeks and are fraught with difficulties, including requirements for high temperatures, pressures, and fluid volumes, risks of leakage and equipment failure, and imprecise initial conditions. Flow-related measurements are generally dependent not only on the applied fluids and pressures, but also on the history of the sample. Any tests preferably should begin with the sample in a native state, but this state is difficult to achieve once the sample has been removed from its original environment. Some rock cores (e.g., oil-bearing unconsolidated sands) deform as they are retrieved from the surface from the high-pressure downhole environment. Much of this deformation is attributable to gases evolving out of solution, expanding and escaping from the core sample. This expansion creates zones of high porosity as grains move around to create escape paths for the gas. The deformation results in an over-estimation of porosity and permeability values, thus making it difficult to determine the original petrophysical properties for the formation, both static (e.g., porosity, permeability and formation factor) and dynamic (e.g., relative permeability, capillary pressure and Archie's saturation exponent). Conventional laboratory methods do not address this issue as physical recompaction techniques used in such methods do not return the sample to its original condition.
It should be understood that the drawings and corresponding detailed description do not limit the disclosure, but on the contrary, they provide the foundation for understanding all modifications, equivalents, and alternatives falling within the scope of the appended claims.